Monostable fluidic switch

ABSTRACT

MONOSTABLE OPERATION OF A SUPERSONIC FLUIDIC SWITCH IS DISCLOSED. FLUID FROM A PRESSURIZED SOURCE IS INJECTED INTO A REACTION CHAMBER AT SUPERSONIC VELOCITY. EITHER BY MEANS OF OFFSETTING ONE WALL ONLY OF THE CHAMBER AT THE THROAT OF THE INJECTION NOZZLE AND/OR BY THE CREATION OF AN ARTIFICIAL AMBIENT PRESSURE WITHIN AND AT ONE SIDE OF THE CHAMBER. THE FLUID JET WILL BE CAUSED TO NORMALLY ATTACH TO ONE WALL OF THE CHAMBER. MONOSTABLE SWITCHING   ACTION IS ACHIEVED BY INCREASING THE PRESSURE WITHIN THE RECIRCULATION REGION PRODUCED ALONG THE WALL TO WHICH THE SUPERSONIC JET NORMALLY ATTACHES THEREBY REVERSING THE TRANSVERSE PRESSURE UNBALANCE ACROSS THE JET.

P 21, 1 R. v. THOMPSON MONOSTABLE FLUIDIC SWITCH Filed Sept. 5. 1969 SECTIONS SHOCK WAVES---- ENGINE EXHAUST INVENTOR RAYMOND V- THOMPSON ATTORN EYS United States Patent 3,606,901 MONOSTABLE FLUIDIC SWITCH Raymond V. Thompson, Simsbury, Conn., assignor to Chandler Evans, Inc., West Hartford, Conn. Filed Sept. 5, 1969, Ser. No. 855,672 Int. Cl. F15c 1/10 US. Cl. 13781.5 12 Claims ABSTRACT OF THE DISCLOSURE Monostable operation of a supersonic fluidic switch is disclosed. Fluid from a pressurized source is injected into a reaction chamber at supersonic velocity. Either by means of offsetting one wall only of the chamber at the throat of the injection nozzle and/or by the creation of an artificial ambient pressure within and at one side of the chamber. The fluid jet will be caused to normally attach to one wall of the chamber. Monostable switching action is achieved by increasing the pressure within the recirculation region produced along the wall to which the supersonic jet normally attaches thereby reversing the transverse pressure unbalance across the jet.

BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to fluidics. More particularly, the present invention relates to fluid devices such as switches and relays which operate with supersonic flow and which are monostable in nature. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.

(2) Description of the prior art The rapid development of devices such as ballistic missiles in which the mechanism for controlling the functions or movements of the device must react rapidly, be highly reliable and be of light weight has caused considerable attention to be given to the subject of fluidics. Fluidics may be defined as the field relating to the control of apparatus by jets of high velocity fluid.

One of the most important devices in the field of fluidics is the fluid relay or switch. Prior art fluid relays comprise a casing defining a reaction chamber or operating region which is narrower at its entrance end than at its discharge end. The casing is formed with an inlet port, through which a power or main stream of fluid is discharged into the narrow end of the reaction chamber, and will have an outlet passage or passages leading from the other or wide end of the reaction chamber. In previous fluid relays the diverging walls of the reaction chamber at both sides of the inlet port were offset from the discharge end of the inlet port whereby the narrow end of the reaction chamber was wider than the inlet port. One and usually two control ports, the ports facing one another and having axes which are oriented transversely to the axis of the inlet port, are typically located closely adjacent to the narrow end of the reaction chamber. The inlet and control ports are connectable to supplies of gas under pressure, the usual operating pressure being somewhere between 5 and 15 p.s.i.

In the operation of the above-described prior art fluid relays, a low velocity stream of fluid issuing from the inlet port moves into the divergent reaction chamber and, owing to irregularities in the flow and asymmetry in the shape of the chamber, the fluid stream bends to one side or the other before flowing into an outlet passage nearer that side. It is to be noted that, due to the subsonic velocity of the fluid, no substantial expansion of the power stream or jet will occur when the stream is discharged into the 3,606,901 Patented Sept. 21, 1971 reaction chamber. By admitting fluid under pressure to the control port on the side of the chamber toward which the mam or power stream of fluid discharging from the inlet port is bent, the power stream can be caused to swing to the opposite wall of the reaction chamber so that it is then directed into the other outlet passage. A comparatively small quantity of low pressure control fluid can thus control a jet powerful enough to perform control or propulsion functions when directed in the appropriate outlet passage.

The above briefly described low pressure relays of the prior art operate by the aid of the Coanda effect. This effect may be briefly stated as a tendency of a fluid in motion to flow along a surface and follow the contour of a surface even when the surface is curved away from the direction of flow of the fluid. In employing the Coanda effect, it has been necessary to utilize fluid at comparatively low pressure whereby the velocity of the power stream issuing from the inlet port is low and subsonic. Thus, the pressure in the power stream issuing from the inlet port of the prior art fluid relays is super-atmospheric and, because the pressure is super-atmospheric and also because of the tendency of the stream of fluid to adhere to one wall or the other of the reaction chamber, it has been necessary to form prior art fluid relays in such a manner that the stream issuing from the inlet port cannot contact either wall of the chamber immediately as it leaves the inlet port. This design requirement is necessary in order to provide a space within which the control fluid may operate transversely against the stream issuing from the inlet port. Thus, as described above, in order to provide the reaction space, prior art fluid relays are formed in such a manner that the narrow end of the chamber is wider than thedischarge end of the port through which the power stream enters the reaction chamber. This is usually referred to as offsetting the control ports and the amount by which the control ports are offset is usually referred to as set back. In summary, conventional prior art fluid relays operate mainly on simple mechanical principles whereby the pressure of the control fluid simply pushes the power stream of fluid issuing from the inlet port in a tranverse direction and forcibly detaches it from the wall of the chamber along which it was flowing and causes it to move by a form of snap action over to the other side of the chamber where the fluid attaches to the other wall.

Prior art fluid relays of the type briefly described above are incapable of providing output streams with suflicient energy to perform many control functions. Attempts have been made to enhance the power output of fluid relays by increasing the pressure of the fluid and particularly by increasing the pressure to such an extent that the fluid injected into the reaction chamber leaves the inlet port with supersonic velocity. While most prior art attempts to utilize supersonic flow have resulted in unstable devices, particularly when the downstream or back pressure against which the device operated was not constant, a stable and highly eflicient supersonic fluidic switch is described in copending application Ser. No. 786,684 filed by the same inventor on Dec. 24, 1968. The disclosure of copending application Ser. No. 786,684- is incorporated herein by reference. The apparatus disclosed in the said copending application is bistable in nature in that the power stream may be switched to either wall of the reaction chamber and will retain attached to the wall to which it has been directed until switching is again commanded.

While the invention of copending application Ser. No. 786,684 has exceptional utility, there are many applications which require that the high power output stream of supersonic fluid return to a preselected flow mode automatically upon cessation of a control action. Thus,

for example, considering a thrust vector control for a' SUMMARY OF THE INVENTION The present invention overcomes the above-discussed and other disadvantages of the prior art by providing for the monostable operation of supersonic fiuidic switches. Devices in accordance with the present invention are characterized by an inlet port which cooperates with the diverging walls of the reaction chamber to define a convergent-divergent nozzle. The pressure at the source of fluid for the power stream is selected to be sufficiently high that the fluid expanding through the nozzle will attain supersonic velocity. Switching of the supersonic jet is achieved, in monostable operation, by reversing a transverse pressure unbalance created across the jet.

In accordance with a first embodiment of the present invention, the reaction chamber is designed in such a manner as to produce a condition adjacent to the discharge end of the inlet nozzle whereby an oblique shock wave is generated; the shock wave serving to promote attachment of the supersonically flowing fluid to the wall from which the shock wave emanates. As a result of the supersonic flow, boundary layer separation and reattachment will occur and a low pressure recirculation region or vortex will be created on the wall along which the supersonic fluid is flowing. By installing a control port immediate the points of separation and reattachment, control action may be achieved. Thus, by means of a valve in series with the control port, the pressure intermediate the separation and reattachment points of the power stream to the chamber wall may be increased to thereby reverse a transverse pressure unbalance across the stream and cause switching. However, due to the velocity gradient which results in the generation of the aforementioned oblique shock wave, closing of the control port will result in the power stream immediately reattaching to the wall in which the control port is located.

In accordance with the first embodiment of the present invention, the oblique shock wave is produced by offsetting a small distance the chamber wall which has the control port therein; the set back being at the throat of the convergent-divergent inlet nozzle. The opposite wall of the chamber will exhibit the gradual change or flaring from the nozzle which is characteristic of the supersonic switches of copending application Ser. No. 786,684.

Also in accordance with the present invention, monostable operation and/or altitude compensation may be provided through the creation of a region of artificial ambient pressure within the fluidic switches. This artificial ambient will be created adjacent to the opposte wall of the chamber from that along which it is desired to normally have the stream flow. The artificial ambient is created by a combination of forward pressure feed from the power stream source and secondary injection. Creation of the artificial ambient provides a degree of immunity from the large ambient pressure fluctuations which may be imposed on the devices of the present invention when employed in environments such as missiles.

A BRIEF DESCRIPTION OF THE DRAWING The present invention may be better understood and its numerous objects and advantages will become apparcut to those skilled in the art by reference to the accompanying drawing wherein like reference numerals refer to like elements in the two figures and in which:

FIG. 1 is a cross-sectional, top view of a first embodi: ment of the present invention; and

FIG. 2 is a cross-sectional, side view of a second embodiment of the present invention; the embodiment of FIG. 2 being depicted in the environment of a reaction engine control.

DESCRIPTION OFTHE PREFERRED EMBODIMENTS I With reference now to FIG. 1, a monostable fluidic switch in accordance with the present invention is shown.

The switch of FIG. 1 comprises a casing, indicated generally at 10, which is etched or machined to provide a reaction chamber 12. Reaction chamber 12 is defined, in part, by diverging walls 14 and 1 6 and by-an'exit or discharge port 18. The switch of the embodiment of FIG. 1 is also characterized by a convergent-divergent nozzle, the convergent portion of the nozzle being indi-- cated at 20, through which pressurized fluid from a source, not shown, is discharged into reaction chamber 12, the reaction chamber serving as the divergent portion of the inlet nozzle. The pressure P at the upstream end of nozzle 20 is sufficient to impart supersonic velocity to the fluid expanded through nozzle 20 into chamber 12.

The embodiment of FIG. 1 is also characterized by a control port 22 in wall 16. Communication between control port 22 and the ambient atmosphere 'is via passage 23 formed in casing 10. A control valve 24 is disposed in passage 23 whereby port 22 may either be placed a the ambient pressure'P or isolated therefrom.

Wall 14 of reaction chamber 12, in accordance with the teachings of copending application 786,684, diverges from the exit end of nozzle 20 without any set back. However, wall 16 of chamber 12 is oflset'by a small amount at section A-A as shown. The reason for theset back of wall 16 will become obvious from the description of the operation of the invention to follow.

As previously noted, the applied pressure P is of suflicient magnitude to cause sonic flow at the throat section AA of nozzle 20 against the ambient back pressure P Due to the sonic flow condition, fluid discharged from nozzle 20 will expand into the divergent reaction chamber completely filling the chamber to section BB and forming an oblique shock wave X emanating from the corner tiating the corner resulting from the set back of wall 16.

As a consequence of the transverse acceleration of the fluid expanding through nozzle 20, such transverse acceleration resulting from the set back of wall 16, the flow will separate from wall 14 at section BB as shown. The localized shock wave generated as a result of the separation of flow from wall 14 is indicated at Y.

Since the jet is caused to separate from wall 14, and also as a result of the Coanda effect, the power stream will attach to and thus flow along wall 16. Due to the supersonic flow phenomena, but also due to the back pressure P separation of the fluid stream from wall 16 will occur at section C--C, the separation producing'another localized shock wave Z. As a result of turbulence and entrainment activity between wall 16 at section D*-D thereby enclosing a recirculation or vortex region of average distributed pressure P the pressure P being less than P As previously noted, the control port 22 is positioned intermediate the points of separation and reattachment so as to be in communication with the recirculation region. It is to be further noted that the pressure within the recir culation region is alsoless than the pressure P in chamber 12 caused by entrainment activity on the free surface of the jet; P being less than P due to entrainment. The 7 pressure differential between P and the recirculation region pressure P will aid in holding the jet against wallv 16 until such time as switching is commanded.

When it is desired to switch the jet from wall *16 to wall 14, control port 22 will be placed into communication with the ambient atmosphere, or other suitable pressurized source, by means of opening valve 24. Opening of the control port to the source of pressurized fluid disrupts the existing condition of stability by raising the pressure in the recirculation region from P to P and, since P is greater than P the power stream will be switched to wall 14 by reversal of the transverse pressure differential. When switched to wall '14, the power stream will attach thereto and a new recirculation region will be formed along wall 14. With valve 24 open, the openvortex in chamber 12 resulting from entrainment activity on the free surface of the jet, which vortex had previously produced the chamber pressure P will be disrupted. Accordingly, with valve 24 open and the jet switched to wall 14, the chamber pressure will become P where A' A" A- Reclosure of valve 24 will cause P to decrease toward P since the disruption of the open vortex, caused by fluid entering the chamber through control port 22, will be terminated. Accordingly, the jet will be caused to return to wall 16 due to the combined effects of transverse pressure unbalance and set back orientation. That is, closing of control valve 24 will reduce the pressure unbalance to the point where it is unable to overcome the transverse acceleration forces, the jet will return to wall 16 and the original transverse pressure unbalance P P will be reestablished.

To summarize operation of the embodiment of FIG. 1, the set back of wall 16 at section AA permits transverse acceleration of the power stream at its point of entry to reaction chamber 12 and thereby orients the velocity vector along wall 16 causing sufiicient bias to permit the above-described monostable operation. The AP across the inlet nozzle and the back pressure P are critical design factors in that these parameters control the size of the recirculation region. If the recirculation region is too small, attachment of the jet to wall '16 may not be maintained.

The embodiment of the present invention shown in FIG. 2 operates in essentially the same manner as that of the FIG. 1 embodiment. However, the FIG. 2 embodiment is provided with a flow splitter 30 which divides the outlet port into a pair of channels 32 and 34. Considering an engine environment, the direction of the power stream through channel 32 will cause the power stream to impinge transversely upon the engine exhaust, at pressure P and thus will permit thrust vector control. The direction of a fluid through outlet channel 34 will permit discharge or dumping into the ambient atmosphere and may provide a transverse stream of fluid for steering purposes. Considered in the sense of monostable operation, thrust vector control is the stable control mode. It is, of course, to be understood that the device may be rendered inoperative by interrupting the communication between the source and nozzle 20 by means not shown.

As in the case of the FIG. 1 embodiment, gas is expanded via the nozzle 20- causing separation and reattachment of the boundary layer along wall 16; presuming that valve 24 is initially closed. Since the ambient pressure P against which the power stream operates will vary with altitude, means in the form of a conduit 36 is provided to feed pressure forward from the power stream source to a point along wall 14 opposite to control port 22. This forward pressure feed loop creates an artificial ambient which, in cooperation with the attachment vortex in the vicinity of the control port, will create a transverse pressure unbalance which will cause the power stream to remain attached to wall 16 unless control action is effected. It is to be noted that conduit 36 includes a stagnation region for converting fluid velocity to pressure.

Obviously, since the ambient pressure P may be at near vacuum, it would be insuflicient to place control port 22 in communication with the ambient atmosphere via valve 24. Accordingly, a conduit 38 extends between the upstream side of valve 24 and a region of pressure P With valve 24 in the open condition, communication is provided between the control port 22 and the engine exhaust, P being relatively constant and higher than either the artificial ambient or P Opening of valve 24 will, accordingly, unbalance the pressure differential across the power stream and cause switching of the power stream to wall 14 and channel 34. Reclosing of valve 24 will result in the power stream returning to wall 16 and channel 32. It is, of course, to be recognized that conduits 36 and 38 may be replaced by auxiliary sources of pressurized gas.

With further regard to the embodiment of FIG. 2, it is to be observed that satisfactory operation may be achieved Without the set back of wall 16. However, while attachment of the jet to wall 16 may be maintained without any transverse acceleration solely as a result of the transverse pressure unbalance between the artificial ambient and recirculation region pressure, it is considered desirable to minimize the gas flow employed for creating the artificial ambient by having some set back. Thus, switch design will usually call for balancing the flow rate through conduit 36 against the set back of wall 16 to achieve optimum performance with minimum gas expenditure.

It is also to be noted that the embodiment of FIG. 2 operates into a differential back pressure (P and P Such operation, which has not previously been possible due to stability problems, is permitted by the creation of the artificial ambient.

While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the present invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

What is claimed is: 1. A monostable fluidic device comprising: an operating region defined in part by a pair of diverging side walls; convergent nozzle means, said nozzle means communicating with the narrow end of said operating region and cooperating with said side walls to define a convergent-divergent nozzle for discharging a stream of fluid into said operating region at supersonic velocity; control means for causing a stream of fluid discharged into said operating region to normally flow along a first of said side walls, the supersonic velocity of the fluid resulting in separation and reattachment of the fluid stream to said first side wall, a low pressure recirculation region thereby being established between said points of separation and reattachment and a transverse pressure unbalance being thus created across the fluid stream in the vicinity of said recirculation region; a control port positioned in said first side wall between said points of separation and reattachment; and normally closed valve means for selectively supplying fluid at a pressure in excess of that established in said recirculation region to said control port, opening of said valve means reversing the pressure unbalance across the fluid stream whereby the stream may be selectively switched to a flow path along said second side wall, reclosing of said valve means causing the stream to return to said first wall under the influence of said control means.

2. The apparatus of claim 1 wherein said valve means comprises:

a valve, the downstream side of said valve being in communication with said port; and means connecting the upstream side of said valve to a source of fluid.

3. The apparatus of claim 2 wherein said control means comprises: i 7

means for creating an artificial ambient atmosphere Within said operating region intermediate the length of and adjacent to said second wall.

4.The apparatus of claim 3 wherein said means for creating an artificial ambient comprises:

a second port located in said second wall oppositely of said recirculation region; and

conduit means providing communication between said second port and the upstream side of said nozzle means.

5. The apparatus of claim 4 wherein said control means further comprises:

a set back in said first wall of said operating region, said set back being positioned at the throat of said convergent-divergent nozzle and generating a velocity gradient in the fluid expanding through said nozzle, said velocity gradient being oriented so as to cause the fluid to attach to said first wall.

6. The apparatus of claim 4 further comprising:

flow diverter means positioned at the wide end of said operating region, said diverter means cooperating with said side walls to define a pair of outlet ports from said operating region.

7. The apparatus of claim 6 wherein said means connected to the upstream side of said valve comprises:

a conduit having a first end connected to said valve and a second end in communication with the back pressure against which the device is operating.

8. The apparatus of claim 2 wherein said means connected to the upstream side of said valve comprises:

a conduit having a first end connected to said valve and a second end in communication with the back pressure against which the device is operating.

9. The apparatus of claim 8 wherein said control means comprises:

a set back in said first wall of said operating region,- said set back being positioned at the throat of said convergent-divergent nozzle and generating a velocity gradient in the fluid expanding through said nozzle, said velocity gradient being oriented so as to cause the fluid to attach to said first wall.

10. The apparatus of claim 1 wherein said control means comprises:

a set back in said first wall of said operating region, said set back being positioned at the throat ofsaid convergent-divergent nozzle and generating a velocity gradient in the fluid expanding through said nozzle, said velocity gradient being oriented so as to cause the fluid to attach to said first wall.

11. The apparatus of claim 1 wherein said control means comprises:

means for creating an artificial ambient atmosphere within said operating region intermediate the length of and adjacent to said second wall.

12. The apparatus of claim 11 wherein said control means further comprises:

a set back in said first wall of said operating region, said set back being positioned at the throat of said convergent-divergent nozzle and generating a velocity gradient in the fluid expanding through said'nozzle, said velocity gradient being oriented so as to cause the fluid to attach to said first wall.

References Cited UNITED STATES PATENTS 3,143,856 8/1964 Hausmann 13781.5X 3,415,262 12/1968 Chatman 137-815 3,492,920 2/1970 Czajkowski et al. 13781.5 3,508,579 4/1970 Jones l3781.5X

WILLIAM R. CLINE, Primary Examiner PO-1O5O UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 606 a Dated October 197].

Inventor) Raymond V. Thompson It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 9, change "in" to -into- Column 2, line 66, change "retain" to -remain-- Column 4, line 28, after "22" insert --located-- Column 4, line 63, after "16" insert --and the power stream,

the jet will reattach to wall 16-- Signed and sealed this 18th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHFIR,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

